Heads of red cabbage, carrot tops and annual flowers complement one another in the author’s former garden. (Barbara Damrosch)

As gardeners, we cast our plants in different roles. “Because you’re so beautiful,” we tell a rosebush, “I’m going to give you the best-dug bed I can, with loose, fertile soil.” We offer a tomato plant the same cushy setting, “because you’re going to taste so good.”

Roses and tomatoes bear fruits that are rich in vitamin C. But should they be bedfellows? No.

It’s tempting to add fast-maturing edible plants to existing ornamental beds, but unless you choose the companions carefully, the results can be disappointing all around.

The rosebush won’t share its space well with the tomato plant, but you might underplant roses with forget-me-nots, sweet alyssum or some other shallow-rooted flower — maybe even a quick edible crop such as arugula. But nothing big and hungry.

Perennial fruit such as blueberries or a perennial vegetable such as asparagus needs its own space.

A mighty vegetable such as the stately, spiky artichoke might hold its own, but would the elegant, blue-green Tuscan kale? Maybe not. A frilly lettuce border would work if you aim to let it bolt, because the flower clusters it sends up are pretty in their own right. But the theft of heads for salad would leave empty spots. Maybe you could replace those with new lettuce plants, as do the dedicated gardeners that tend the legendary vegetable plots at the Chateau de Villandry in France. You, that is — not busy, overcommitted me.

Years ago my husband and I set about to plant a garden that would visually combine edibles and flowers. We put it in the middle of the lawn, between the food garden and the area where we grew most of our flowers — a…